Ramadan is in its third week now, and the required dawn-to-dusk fasting often feels like a daily miniâ€“marathon. By late afternoon, hunger and thirst have sucked me dry, leaving me sleepy, slow-minded, and sometimes short-tempered.

I know that the purpose of fasting is spiritualâ€”God will reward us in the next lifeâ€”but in this lifetime, fasting sometimes makes me an ineffective, irritable person. So I was excited to learn that Harvard psychiatrist John Ratey, MD, had spoken at a recent Renaissance Weekend event about how caloric restriction can improve brain function.

I emailed Dr. Ratey to find out if those benefits might extend to religious fasting, and he sent me a 2006 paper on the brain functioning of men during the Ramadan fast. The researchers studied a small group of healthy men during and after the holy month, looking at their brain activity via functional magnetic resonance imaging (fMRI). They concluded that â€œall individual results showed consistent and significant increase of activity in the motor cortex during fasting.â€

That research builds on the work of other scientists, including Mark Mattson, PhD, who heads a neuroscience lab at the NIHâ€™s National Institute on Aging. Mattson has done important research on how dietary restrictions can significantly protect the brain from degenerative diseases like Alzheimerâ€™s or Parkinsonâ€™s.

In 2003, Mattson and others reported that rats deprived of food every other day, or restricted to a diet at 30% to 50% of normal calorie levels, showed not only decreased heart rates and blood pressure, but also â€œyoungerâ€ brains, with â€œnumerous age-related changes in gene expression.â€

Mattson and his colleagues also shared data from research on humans, which shows that populations with higher caloric intakesâ€”such as the United States and Europeâ€”have a greater prevalence of Alzheimerâ€™s than do populations that eat lessâ€”such as China and Japan. The authors speculate that humans may have adapted to conditions of feast and famine; the stress of having little food, they write, â€œmay induce changes in gene expression that result in adaptive changes in cellular metabolism and the increased ability of the organism to reduce stress.â€

Although this research is relatively new, with many questions left unanswered, the authors conclude that â€œit seems a safe bet that if people would incorporate a spartan approach to food intake into their lifestyles, this would greatly reduce the incidence of Alzheimerâ€™s, Parkinsonâ€™s and stroke.â€ (Of course, how this recommendation translates for individual people remains almost a complete unknown; consult with your own doctor before restricting your diet in dramatic ways.)

But hereâ€™s the hard part: Although we know eating too much leads to all sorts of health problems, â€œit has proven very difficult to successfully implement prolonged dietary-restriction regimens,â€ reports Mattson and his team. Information and doctorâ€™s orders are rarely enough motivation.

This last observation gave me hope, because it seemed the authors were overlooking the role of religion; it can inspire people in ways information or experts donâ€™t. Would I be undergoing this rigorous month of fasting unless I believed strongly it was the right thing for me to do? Probably not. And the same goes for millions of Muslims around the world.

And many other religions include fasting or dietary restrictions as part of their religious observances. Members of the Church of Jesus Christ of Latter-Day Saints, or Mormons, for example, fast one Sunday a month. The Orthodox Church in America notes five separate fasting seasons on its website, in addition to individual fast days; during some of these fasts, all food is restricted, and during other fasts, only certain foods are off-limits. Some Roman Catholics abstain from meat on Fridays, and all do during Lent. Many types of Buddhist monks abide by a code that prohibits eating after noon each day.

Science may only now be discovering that some of these religious practices, both ancient and modern, offer nourishment not just for the soul, but for the body as well.